Program 13 deals with the law of physics which states that energy is neither created nor destroyed. Program 14 deals with potential energy and the powerful model that this concept has become for understanding why the world has worked the same way since the beginning of time. Program 15 likens the universe to a perpetual clock and applies the principle of conservation of momentum to explain why the universe continues to operate. The same principle is also applied to an analysis of collisions. Program 16 explains that the restoring force and inertia of any stable mechanical system causes objects to execute simple harmonic motion. Uses computer animation sequences, historical reenactments, and close-up photography of experiments.